Vol. 3B 18-23
PERFORMANCE MONITORING
18.5
PERFORMANCE MONITORING (45 NM AND 32 NM INTEL
®
ATOM
™
PROCESSORS)
45 nm and 32 nm Intel Atom processors report architectural performance monitoring versionID = 3 (supporting
the aggregate capabilities of versionID 1, 2, and 3; see Section 18.2.3) and a host of non-architectural monitoring
capabilities. These 45 nm and 32 nm Intel Atom processors provide two general-purpose performance counters
(IA32_PMC0, IA32_PMC1) and three fixed-function performance counters (IA32_FIXED_CTR0,
IA32_FIXED_CTR1, IA32_FIXED_CTR2).
Non-architectural performance monitoring in Intel Atom processor family uses the IA32_PERFEVTSELx MSR to
configure a set of non-architecture performance monitoring events to be counted by the corresponding general-
purpose performance counter. The list of non-architectural performance monitoring events is listed in Table 19-26.
Architectural and non-architectural performance monitoring events in 45 nm and 32 nm Intel Atom processors
support thread qualification using bit 21 (AnyThread) of IA32_PERFEVTSELx MSR, i.e. if
IA32_PERFEVTSELx.AnyThread =1, event counts include monitored conditions due to either logical processors in
the same processor core.
The bit fields within each IA32_PERFEVTSELx MSR are defined in Figure 18-6 and described in Section 18.2.1.1 and
Section 18.2.3.
Valid event mask (Umask) bits are listed in Chapter 19. The UMASK field may contain sub-fields that provide the
same qualifying actions like those listed in Table 18-2, Table 18-3, Table 18-4, and Table 18-5. One or more of
these sub-fields may apply to specific events on an event-by-event basis. Details are listed in Table 19-26 in
Chapter 19, “Performance-Monitoring Events.” Precise Event Based Monitoring is supported using IA32_PMC0 (see
also Section 17.4.9, “BTS and DS Save Area”).
18.6
PERFORMANCE MONITORING FOR SILVERMONT MICROARCHITECTURE
Intel processors based on the Silvermont microarchitecture report architectural performance monitoring versionID
= 3 (see Section 18.2.3) and a host of non-architectural monitoring capabilities. Intel processors based on the
Silvermont microarchitecture provide two general-purpose performance counters (IA32_PMC0, IA32_PMC1) and
three fixed-function performance counters (IA32_FIXED_CTR0, IA32_FIXED_CTR1, IA32_FIXED_CTR2). Intel
Atom processors based on the Airmont microarchitecture support the same performance monitoring capabilities as
those based on the Silvermont microarchitecture.
Non-architectural performance monitoring in the Silvermont microarchitecture uses the IA32_PERFEVTSELx MSR
to configure a set of non-architecture performance monitoring events to be counted by the corresponding general-
purpose performance counter. The list of non-architectural performance monitoring events is listed in Table 19-25.
The bit fields (except bit 21) within each IA32_PERFEVTSELx MSR are defined in Figure 18-6 and described in
Section 18.2.1.1 and Section 18.2.3. Architectural and non-architectural performance monitoring events in the
Silvermont microarchitecture ignore the AnyThread qualification regardless of its setting in IA32_PERFEVTSELx
MSR.
18.6.1
Enhancements of Performance Monitoring in the Processor Core
The notable enhancements in the monitoring of performance events in the processor core include:
•
The width of counter reported by CPUID.0AH:EAX[23:16] is 40 bits.
•
Off-core response counting facility. This facility in the processor core allows software to count certain
transaction responses between the processor core to sub-systems outside the processor core (uncore).
Counting off-core response requires additional event qualification configuration facility in conjunction with
IA32_PERFEVTSELx. Two off-core response MSRs are provided to use in conjunction with specific event codes
that must be specified with IA32_PERFEVTSELx.
•
Average request latency measurement. The off-core response counting facility can be combined to use two
performance counters to count the occurrences and weighted cycles of transaction requests.